The 3 stars, if I am honest, are padded out with sentiment. I am a massive fan of Kurt Vonnegut and have been ever since reading Slaughterhouse-5 about 35 years ago. (Why is this not on kindle! Get on the case amazon!) However I seldom enjoy reading short stories.... Some of Vonnegut's, in Welcome To The Monkeyhouse for instance, are fine. I enjoyed collections like Wampeters, Foma, and Granfalloons rather more.
I really think there were probably sound reasons why these stories were "previously unpublished..." and there's a clue right at the beginning of the text. This is a reproduction of a letter from Kurt to a friend written in the 1950s which prefaces the stories. The gist of what he says is "I write because it earns me and my agent and publishers money". No quarrel with that but someone ought to have exercised some quality control over these stories. The inclusion of this preface does rather feel like a bit of a two-fingered salute to the reader (i.e. "we published this for the money, not because we really felt the stories warranted it). My rejoinder would be if you're a Vonnegut completist try and borrow a library copy, and if not I really think you're going to find these disappointing. Read Slaughterhouse-5 instead!
The only really good line was in a story where the mother of a naive wealthy young person realises that the one great thing that money _can_ buy you is "eternal childhood". In the sense of not having to worry much about the world, grubby poor people, etc. Not madly original though, is it?